The present invention relates to intraocular lenses and particularly to foldable intraocular lenses.
For many years, the predominant method of treating a diseased lens is to remove the lens and replace it with an intraocular lens ("IOL"). Two surgical procedures are preferred for removing the diseased lens: extracapsular cataract extraction and phacoemulsification. Extracapsular cataract extraction involves removing the lens in a relatively intact condition by use of a vectus or similar surgical instrument. Phacoemulsification involves contacting the lens with the vibrating cutting tip of an ultrasonically driven surgical handpiece to emulsify the lens, thereby allowing the emulsified lens to be aspirated from the eye. Both surgical procedures require that the anterior lens capsule be cut to allow access to the lens itself and to allow the implantation of the replacement lens, and because the capsule bag is used to hold or retain the IOL in place after surgery, the opening should be as small as possible. Although extracapsular cataract extraction has been the preferred surgical technique, phacoemulsification is becoming increasingly popular, in part because of the relatively small (around 3 millimeters) tunnel incision that is used with phacoemulsification.
A typical IOL comprises an artificial lens ("optic") and at least one support member ("haptic") for positioning the IOL within the capsular bag. The diameter of the optic varies depending on the design of the IOL, but an optic diameter of around 5 millimeters (mm) to 6 mm is most common. When the surgical technique used is extracapsular cataract extraction, inserting the IOL through the relatively large incision presents no particular difficulties. However, when the surgical procedure used in phacoemulsification, the surgeon typically must widen the initial 3 mm tunnel incision enough to allow the IOL to be inserted into the capsular bag. Enlarging the incision reduces one of the advantages of phacoemulsification because of the possibility for postoperative complications associated with large incision ocular surgery, including induced astigmatism. Therefore, rollable or foldable IOL's have been developed that can be inserted into the capsular bag with minimal widening of the phacoemulsification incision.
As discussed in U.S. Pat. Nos. 4,573,998, 4,619,657, 4,834,750 and 4,919,130, the entire contents of which is incorporated herein in its entirety by reference, foldable IOL's generally are made from polyurethane elastomers, silicone elastomers, hydrogel polymer collagen compounds or organic or synthetic gel compounds. The lens is rolled, compressed or crushed by a special syringe or forceps and placed into the capsular bag without enlarging the incision. While these IOL's and insertion devices work well, the insertion devices are bulky and require practice to master their use.
A second generation of foldable IOL's have recently been introduced that are made from monomers derived from acrylacrylate or methacrylates and a crosslinking agent. Such monomers are described more fully in copending and commonly assigned U.S. patent application Ser. No. 07/879,237, the entire contents of which is incorporated by reference. Such materials are advantageous because they have higher refractive indices and, hence, allow the IOL to be thinner and fold more easily.
Prior to the present invention, to implant IOL's made from such acrylic materials, a special duckbill forceps with rounded jaws that will not close together completely (so as not to press the sides of the folded IOL together) was used. However, these forceps cannot, by themselves, fold the IOL, and the surgeon must hold the IOL with a second needle-nose or tying forceps while enveloping and folding the IOL with the duckbill forceps. This technique, while reliable, requires the use of two hands and a great deal of practice to master.
One IOL folder disclosed in U.S. Pat. No. 5,100,410 uses a pair of opposing jaws that when pressed together folds the IOL within a pair of duckbill forceps. However, the recessed jaws of the folder disclosed in this patent requires that the forceps be held in place on either side of the lens during folding operation, making it difficult for one person (such as the nurse) to fold the IOL while another person (such as the surgeon) holds the forceps.
Another IOL folder disclosed in U.S. Pat. No. 5,139,501 uses a base with a fixed jaw and an opposing, movable jaw. The IOL is placed between the jaws and the movable jaw is pressed toward the fixed jaw, thereby folding the soft IOL. However, this folder must be assembled from several pieces, increasing its manufacturing cost.
Accordingly, a need continues to exist for an inexpensive, one-handed device that will fold easily a soft IOL.